1. Field of the Invention
This invention relates in general to a spray-dried composition prepared by spray drying a mixture of a urea-formaldehyde resin and a lignosulfonate, to the method of preparing the composition, to fertilizers containing the compositions and to the method of preparing such fertilizers. The composition of this invention is useful as a delayed release fertilizer and is also useful as a fertilizer carrier, as a replacement for expanded vermiculite-based fertilizers.
2. Description of Related Art
Slow release nitrogen fertilizers based on urea-formaldehyde resins are known in the art. For example, Darden, U.S. Pat. No. 2,766,283 describes fertilizer compositions based on urea-formaldehyde resins. The urea and formaldehyde are reacted in the presence of water, and at the conclusion of the reaction, the product is neutralized and separated by filtration, by centrifuging, or by another suitable method. Darden does not disclose spray-drying the urea-formaldehyde resin fertilizer composition and does not disclose the use of a lignosulfonate in the composition.
It is also known that lignosulfonate and urea-formaldehyde compositions can be used to improve the wet-strength of paper. Keim, U.S. Pat. No. 2,622,979 disclose lignin sulfonate-modified urea-formaldehyde resins prepared by reacting urea-formaldehyde and a lignin sulfonate under controlled conditions. This modified resin then is incorporated into a paper stock and improves the wet-strength properties of the subsequently produced paper. The lignin sulfonate-modified urea-formaldehyde resin of Keim is not spray-dried and is not disclosed to be useful as a fertilizer or fertilizer carrier.
Mills, U.S. Pat. No. 2,845,397, teaches that when Kraft lignin is treated with urea, or derivatives of urea, and formaldehyde prior to mixing with a rubber latex and coagulating, rubber products having improved abrasion resistance are produced. The so-modified lignin composition is mixed with an alkaline rubber latex and the treated lignin and rubber coagulate is recovered by spray-drying or coprecipitating. Mills does not disclose preparing a spray-dried mixture of a lignosulfonate and a urea-formaldehyde resin for use as a fertilizer or fertilizer carrier.
Christ, U.S. Pat. No. 3,076,772, discloses an alkaline resinous adhesive comprised of urea, phenol and formaldehyde reacted in the presence of an alkali metal base catalyst such as sodium hydroxide. The phenol-urea-formaldehyde resin then is reacted with a sulfite waste liquor, such as lignosulfonate, and the resulting composition is used in making particleboard.
Bornstein, U.S. Pat. No. 4,130,515, discloses a process for preparing a thermosetting resin composition which comprises copolymerizing a lignosulfonate salt, melamine, and an aldehyde. The resin prepared by Bornstein is useful in binding consolidated cellulosic particles to form a board-like product. Edler, in U.S. Pat. Nos. 4,194,997 and 4,244,846, discloses adhesive compositions comprising mixtures of urea-formaldehyde resins and lignosulfonate useful in the production of particleboard.
Finally, Detroit, in U.S. Pat. Nos. 4,752,317, 4,756,738 and 4,789,391, discloses lignosulfonate-acrylonitrile graft copolymers which provide slow release of urea fertilizers. The patents to Detroit disclose that the fertilizer may be modified to provide controlled nutrient release by controlling the solubility of the fertilizer.
An article by Vorob'eva titled "The Effect of Salt Media on the Lignosulfonate Urea Formaldehyde Resin Polycomplex" describes experiments demonstrating the use of a urea-formaldehyde resin, and its mixture with lignosulfonate, to produce granulated potassium chloride fertilizers. Use of the resin provides improved granule strength and slow release properties. The lignosulfonate and urea-formaldehyde compositions in the Russian paper are dried either at room temperature, or in an oven at 110.degree. C. The Russian article does not disclose a spray-dried lignosulfonate and urea-formaldehyde composition.